Can you tell more about the bacteria experiment?
some quick ideas - thinking oud loud:
- An Arduino can measure environmental params easily - temperature, humidity, pressure
- there are libraries for gas sensors
- there is code on the forum for PH measurements.
Furthermore assuming the bacteria are in a petri dish you can illuminate them with diferent colors (including IR and UV led) of light and measure
- reflection, absorbtion and pass through with light sensors. =>> absorption = LIGHTIN - reflection - passthrough
- You can switch a laser "burning" the bacteria and measure new gasses.
All these measurements will change over time (or not) which indicates growthrate or productivity or ...
Of course you need to build up calibration and reference tables to interpret the data you get
(no microbiologist so all disclaimers apply